Ultra-violet-transmitting glass and process of making the same



Patented OcL ZI 1930 UNITED STA TEVS PATENT OFFICE BERNARD LONG, OF PARIS, FRANCE, ASSIGNOR TO SCCIETE ANONYME DES MANUFAC TUBES DES GLACES & PBOIDUITS CHIMIQUES DE SAIN'T-GOBAIQN OF PARIS, FRANCE ULTRA-'VIOLET-TRANSMITTING GLAssAm) zenocnss on maxme THE SAME No Drawing. Application filed May 24, 1928, Serial No. 280,391, and in France June 4, 1927.

5 posure to such rays, and to a process of manufacturing the same.

7 It is essentialfor ultra violet transmission that the iron content be reduced to very low limit. Iron cannot be convenienty eliminated 1o entirely, and therefore it has been proposed to melt such glass under a reducing condition, so that such iron as may be in the glass will be in a ferrous condition. I Under the action of the short waves, however, such v 15 ferrous iron is apparently converted into ferric iron with the loss of the desired transparency.

I have found that this change in the condition of the iron may be retarded by introducing into the glass batch a small percentage of manganese dioxide. When the glass is melted under reducing conditions, the manganese is reduced to a sub-oxide. By exposure of the glass to sunlight, this sub-oxide is attacked by any oxygen in the glass and converted to the dioxide before the ferrous iron is converted into ferric iron. While, due to the small quantity ofiron present the resultant glass may have a violet tint after the reoxidation of the manganese, the transmission of the glass for the ultra-violet will not be affected.

' In carrying out my invention I melt quartz, v or a glass batch of the desired ingredient, freed as far as may be desired from iron and under oxidizing conditions and to the batch the yellow tint which would otherwise bGlDlti'ally present due to ferric iron. With the ultra-violet transmission glasses no addition of manganese is needed for neutralizing such initial yellow tint.

Having thus described my invention what I claim is 1. A glass transparent to and" stable against the action of ultra-violet rays of sunlight, containing less than 0.02% of ferric of which manganese is added to neutralize ironand containing manganese in quantities between 0.05% and 0.50%.

2. The hereinbefore described method of fabricating a glass transparent to and stable against the action of ultra-violet rays of sunlight, comprising so melting'such proper raw materials containing 0.05% to 0.50% man ganese dioxide, under reducing conditions that the resultant glass contains ferric iron less than 0.02%.

In testimony whereof I hereunto aflix my signature.

' BERNARD LONG.

containing 0.05% to 0.50% of dioxide manj ganese, under reducing conditions, produced, either by regulation of the furnace, or by the addition of carbonaceous material to the batch and form the resultant glass into sheets The glass having this limited quantity of ferric iron and the ultra-violet transmission I referredto. is not to be confoundediwith the usual window. glasses containing substantial quantities of iron, which are generally melted 

